Refrigeration



E. S. LYNGER REFRIGERATION Nov. 28, 1939.

' Filed Jung 17, 1937, 4 Sheets-S heet 1 A ATTORNEY.

E. S. LYNGER Nov. 28, 1939.

REFRIGERATION Filed June 17, 193'? 4' Sheets-Sheet 2 M mvpw E. S. LYNGER Nov. 28, 1939.

REFRIGERATION Filed June 17, 1 957 4 Sheets-Sheet 3 ORNEY 4 Nov. 28, 1939. E. s. LYNGER 2.1813 6 REFRIGERATION Filed June 17, 1957 4 Sheets-Sheet 4 A ATTORNEY.

Patented Nov. 28, 1939 PATENT OFFICE REFRIGERATION Erik Sigi'rid Lynger, 'Stockholm, Sweden, assignor, by mesne assignments, to Servel, Inc., New

York, N. Y., a corporation of Delaware Application June 17, 1937, Serial No. 148,709

' In Germany July 10, 1936 1-: Claims.

My invention relates to refrigeration, and more particularly to control of refrigeration apparatus.

It is an object of my invention to provide an improved control for refrigerators to initiate defrosting, the control being operative to instigate and terminate automatically the operation required to effect defrosting. I accomplish this by providing a control element which is moved from time to time toward a region of a cooling element or evaporator where frost or ice accumulates thereon, the movement of the control element preferably being automatically effected by a variable operating condition of the refrigerator. Among the variable operating conditions which 5 may be effectively utilized to cause intermittent movement or probing of the control element, for example, are the temperature of the space being cooled or the temperature of a part of the refrigeration system which varies with sufllcient regularity.

Another object of my invention is to utilize such a control element with a device which controls the operation of a refrigeration system, the element preferably being arranged in such a manner that the normal operation of the control device is modified to the extent that the refrigerating effect is reduced when a layer of frost of predetermined thickness has accumulated on the cooling element.

A further object of my invention is to provide such a control elementfto instigate defrosting by heating a cooling element, such heating preferably being effected without disturbing the operation of the refrigeration system.

A still further object of my invention is to effect defrosting by passing h ot gases in a refrigeration system through a cooling element or evaporator on which frost has accumulated.

The above and other objects and. advantages of my invention will be more fully understood from the following description taken in conjunction with the accompanying drawings forming a part of this specification, and of which Fig. 1 diagrammatically illustrates a refrigeration system provided with control embodying my invention; Fig. 2 is an enlarged vertical sectional view illustrating more clearly the control shown in Fig. 1; Fig. 3 is a modification of the control shown in Figs. 1 and 2 whereby defrosting is effected by passing hot gases through a cooling element; Fig. 4 diagrammatically illustrates control similar to that shown in Fig. 3 in which frost is melted by heating a cooling element without disturbing the operation of the refrigeration system; Fig. 5 is a further modification in which a variable operating condition of a part of the refrigeration system is utilized to automatically efiect defrosting; and Fig. 6 is a sectional view taken at line 66 of Fig. 5 to illustrate parts of the control more clearly. 5

Referring to Fig. 1, I have shown my invention in connection with an absorption refrigeration system of a uniform pressure type, generally as described in Patent No. 1,609,334 to von Platen and Munters, which contains an auxiliary pres- 10 sure equalizing gas. It is to be understood, however, that my invention 'can be employed with other types of refrigeration systems.

The system includes a cooling element or evaporator ill disposed in an enclosed space H which 15 may form a food storage compartment of a thermally insulated cabinet 12. A refrigerant fluid, such as ammonia, evaporates in the evaporator 10 and diffuses into an inert gas, such as hydrogen, to produce a refrigerating effect. The resulting gas mixture of ammonia and hydrogen flows from the evaporator 10 through a conduit l4, gas heat exchanger l5, and conduit 16 into an absorber H. In absorber I1 ammonia vapor is absorbed by a suitable liquid absorbent, such 25 as water, which enters through a conduit. [8. The hydrogen, which is practically insoluble and. weak in ammonia, is returned to the upper part of the evaporator 10 through a conduit IS, the gas heat exchanger l5, and a vertical conduit 30 20; and the enriched absorption liquid is conducted from absorber'l'l through a liquid heat exchanger 2| to a coil 22 which is disposed about an electrical heating element 23 extending into the-lower part of a generator 24. 35

By heating coil 22, ammonia vapor and absorption liquid are raised by vapor-lift action through conduit 25 to the upper part of generator 24. Liberated ammonia vapor entering the generator 24 through conduit 25, as well as ammonia vapor 40 expelled from solution in the generator, flows upward into an air-cooled condenser 26. The amammonia has been expelled is conducted from generator 24 through liquid heat exchanger 2| and conduit l8 into the upper part of the absorber. The heat liberated with absorption of 55 -pleted with the bulb tilted when the left-hand cooling medium which flows through a coil 29 which is disposed about and in thermal relation with the absorber. A conduit 30 is connected to the lower part of condenser 26 and to the gas circuit, as at the gas heat exchanger l5, for example, so that any non-condensable gas which may pass into the condenser can flow into the gas circuit and not be trapped in the condenser.

The heating element 23, which is connected to a source of electrical supply and serves as the source of energy for the refrigeration system, is controlled by a mercoid switch 3| which is connected in series relation with the heating element by conductors 32 and 33. Referring more particularly to Fig. 2, the switch 3| is provided with a base plate 34 and a removable cover 35 within which is disposed a bulb 36. The bulb 36 contains a body of mercury 31 and is provided with two spaced depending parts to which are connected the conductors 32 and 33. The bulb 36 is fixed to an inverted U-shaped member 38 which is pivotally mounted at 39 to spaced brackets 40 secured to the base plate 34. The inverted U-shaped member 38 and bulb 36 carried thereby rock about the pivot 39, the electrical circuit being open with the bulb in the position shown in Fig. 2 and the circuit being closed or compart thereof is in the down position and the right-hand part thereof is in the up position.

In order to rock the bulb 36 about the pivot 39 to connect and disconnect the heating element 23 to and from the source of electrical supply, a pin 4| is secured to the side walls of the inverted U- shaped member 38. The pin 4| is in the path of movement of the bifurcated arms 42 of a lever 43 which extends vertically downward through an opening in the base plate 34.

In accordance with my invention the lever 43 and bulb 36 of the switch 3| are controlled in response to a thermal element 44 disposed in the space and this normal control is automatically modified by a control or probing member 45 when a layer of frost of predetermined thickness has accumulated on cooling element Ill. The probing member 45 is associated with the thermal eleconnected to thermal element 44.

ment 44 whereby the member 45 is automatically moved from time to time toward a region of the cooling element to with changes in temperature of the space H.

The mechanism connecting the lever 43, thermal element 44 and probing member 45, to effect control of the refrigeration 'system and also instigate defrosting, includes a capillary tube 46 The tube 46 extends through an insulated wall of cabinet I2 and is connected to a plate 41 to which is secured one end of an expansible bellows 48. Within the bellows 48 is disposed a sleeve 49 having the flanged outer end 50 thereof secured to the opposite end of the bellows. The chamber defined by the closed sleeve 49 and bellows 4B, tube 46 and thermal element 44 constitute an expansible fluid thermostat which is filled with a end thereof fixed to the inner end of sleeve 49.

The rod 52 extends through an opening in a cover member 53 which is mounted on base plate 41, and a coil spring 54 is disposed about rod 52 and 2,181,876 3 ammonia' vaporin absorber I1 is transferred to a bears against the inner end of sleeve 49 and cover member 53. The rod 52 is pivotally connected to the lower end of a vertical lever 55 which is pivoted at 56 to a bracket 51 fixed to cover member 53. The upper end of lever 55 is forked to receive a pin 56 at the outer end of a horizontally movable rod 59.

The rod 59 is journaled in openings formed in a bracket 69 which is U-shaped with one arm.

bent back upon itself and mounted on the cabinet l2 and the other arm extending upward and serving as a support for switch 3|. The rod 59 is provided with a pin 6| which extends into an elongated slot 62 formed in the lower end of lever 43. A pin 63 is fixed to lever 43 and extends downward on the opposite side of rod 59 from the lever 43 to maintain pin 6| in slot 62. To the inner end of rod 59 is rigidly secured a small plate 64 which in turn is connected by a coil spring 65 to the lever 43 at a point above slot 62.

The mechanism thus far described connects the expansible fluid thermostat and the switch 3|, with the lever 43 in effect forming a. continuation of lever 55. The switch 3| is normally controlled in response to the temperature of space N, therefore, to increase or decrease the refrigerating effect produced by cooling element II).

To modify the normal control of switch 3| when a layer of frost of predetermined thickness has accumulated on cooling element It), the outer end of probing member 45 is pivotally connected at 66 to the lever 43. Probing member 45 extends through an opening 61 in an insulated wall of cabinet I 2 and at its inner end is provided with an enlarged head 68 which is preferably formed of rubber or other suitable material. The opening 61 is partly filled with suitable insulating material 69 which is retained in position by an annular sleeve 10.

To the ends of sleeve are fixed collars 1| and 12 having central openings through which the probing member 45 extends. The collars 1| and 12 are provided with additional openings 13 and 14 and are enlarged at their outer ends. Resilient diaphragms and 16 are secured to probing member 45 and their peripheral edges are secured to the collars 1| and 12 by hollow cap members 11 and 18. The hermetically closed space between the diaphragms 15 and 16 may be filled with dry air or suitable liquid, and the space between the cap member 18 and inner wall member 19 of the cabinet I2 is preferably sealed by a gasket 80.

The operation of the control just described is substantially as follows: Assuming that switch 3| is in its circuit open position shown in Fig. 2 and cooling element 0 is substantially defrosted or only covered with a thin layer of frost, the switch 3| will be moved to its circuit closing position when the space H tends to rise above a desired low temperature. In such case the volatile fluid of the expansible fluid thermostat increases in volume and causes bellows 48 to expand. With expansion of bellows 48, rod 52 is moved outward by sleeve 49, and lever 55 is rotated about pivot 56 in a clockwise direction to cause horizontal movement of rod 59 toward the cabinet |2. Due to the provision of the pin and slot connection 6| and 62, lever 43 is also moved toward cabinetlfl whereby movement is imparted to probing member 45.

- The lever 43 is prevented from rotating undermove toward the cooling element a distance to permit sufflcient lateral displacement of lever 43 whereby the left- When the space H tends to fall below the de-' sired low temperature, the volatile fluid in the expansible fluid thermostat becomes reduced in volume, whereby the bellows 48 contracts and spring 54 becomes effective to move rod 52 toward the cabinet |2. With such movement of rod 52, lever 55 is rotated in a counter-clockwise direction to cause horizontal movement of rod 59 away from the cabinet l2. This produces lateral movement of lever 43 away from cabinet l2 so that the right-hand bifurcated arm 42 will contact and move pin 4| and cause member 38 and bulb 36 to rock back to the position shown in Fig. 2. With the bulb 36 now in its circuit open position, the heating element 23 will be disconnected from the source of electrical supply and .the refrigerating efiect produced by cooling element I6 will tend to maintain the space l at the desired low temperature. I

It will' now be understood that switch 3| is controlled in response to a temperature condition affected by cooling element I6, and thatwith changes in temperature in. space H the probing member 45 is automatically moved from time to time toward a region ofthe cooling element. When a layer of frost 9 of predetermined thickness has formed on the cooling element l8 and defrosting is desired, the above described operation is automatically modified inthe following manner. When space H tends to rise above the desired low temperature, rod 59 is moved toward cabinet l2 and probing member 45 is moved toward cooling element In in the same manner as explained above. Due to,- .the formation of frost on cooling element l6, however, the movement of probing member 45 is stopped as soon'as the,

enlarged head 68 contacts the layer of frost. The rod 59 continues to move toward cabinet I with the result that lever 43 is rotated on its pivot 66 in a counter-clockwise direction. With such rotation of-l'ever 43 the left-hand arm 42 at the upper end of the lever is prevented from moving pin 4| and tilting bulb 36 from the circuit open position shown in Fig. 2 to its circuit closing position, as in the normal operation explained above. Even though the'space II is tending to rise above the desired low temperature, therefore, the refrigerating effect is not increased in the normal manner, thereby permitting the temperature of cooling element ID to increase and allow melting of frost. Under these conditions the spring 66 is under tension and is constantly urging the enlarged head 68' of probing member 45 to bear against the layer of frost.

With melting of frost the probing member 45 is moved toward cooling element l6, and, when the cooling elemnt is substantially defrosted, the I movement of the probing member has rotated lever 43 sufficiently in a clockwise direction about the pin 6| to cause the left-hand arm 42 of lever 43 to move pin 4| and rock bulb 36'from its circuit open position to its circuit closing position. The heating element 23 will now be connected to the source of electrical supply and the cooling element IE will again produce a refrigerating effect to lower the'temperature of space II. By melting the frost accumulated on cooling element ID, the latter is rendered more effective to produce refrigeration.

In Fig. 3 I have shown a modification in which refrosting is efiected by passing hot. gases in the refrigeration system through the cooling element. In order to simplify the drawings parts of the system in Fig. 3, which are similar to those in Fig. 1, have been omitted, these parts including the gas heat exchanger l5, absorber liquid heat exchanger 2|, and connections therebetween.

The parts of the system which are shown in Fig. 3

,and similar to those illustrated in Fig. 1 are designated by the same reference numerals.

In Fig. 3 the lower part of condenser 26 is. connected to a conduit 21' which extends downward into a U-shaped trap 8| formed in a conduit 82. The conduit 21 for conducting liquid ammonia to the upper part of cooling element Ill is connected to one-arm of trap 8|. One end of' conduit 82 is connected to vertical conduit 83 through which ammonia vapor flows upward from generator 24 to condenser 26, and the other end thereof is connected to-the upper part of cooling element H). a jacket 84 which may contain a suitable liquid adapted to be heated by an electrical heating element 85. V

During normal operation of the refrigeration system liquid ammonia collects in trap 8| whereby ammonia vapor flowing in conduit 83 passes in the usual manner into condenser 26 in which it is liquefied. The liquid ammonia flows through conduit 21' to trap 8| and thence through'conduit 21 into the upper part of cooling element I where it evaporates and diffuses into hydrogen entering through conduit 26. When it is desired to defrost cooling element 16, the heating element 85 is connected to a source of electrical supply to heat the liquid in jacket 84. By evaporating the liquid intrap 8|, the liquid seal in conduit 82 is quickly broken whereby ammonia vapor flowing upward in conduit 83 passes through conduit 82 directly into the cooling element Ill. The ammonia vapor entering the cooling element heats up the latter and effectively melts frost which has formed on its surfaces.

The heating element 85 may be controlled by a probing member M in a manner. similar to that shown in Fig. 1. The control shown in Fig. 3 differs from that illustrated in Fig. 1, in that the probing member I45 does 'not modify the operation of the switch 3| which controls the generator heating element 23. In this modification the intermittent opening and closing of the electrical circuit associated with switch 3| is utilized to energize from time to time a magnet 86 to cause movement of probing member |-45 toward the cooling element Ill.

In Fig. 3 it will be seen that heating element 23, the windings 81 of magnet 86, and switch 3| are connected in series relation by conductors 88,

, 89, 8,6, and 3! to the source of electrical supply.

One arm of trap 8| is provided with extends through an ally connected at .be a circuit open position,

The diaphragms I15 and I16 are secured at their peripheral edges to collars "I and I12 by hollow cap members I11 and I18, the collar I1I extending through the opening and serving as a sleeve member. The outer end of probing member I45 is provided with a pin ml which extends into a slot I62 formed at the lower end of lever I43. The lever I43 at its upper end is provided with bifurcated arms I42 for rocking a switch 'I3I similar to the switch 3| shown in Fig. 1. The member I38 carrying bulb I36 is pivoted at I39 to a bracket I40 which is supported in any suitable manner. The switch I3I is connected in series relation with heating element 85 by con- 'ductors 94, 95, and 96 to the source of electrical supply.

The magnet 86 is fixed to a U-shaped bracket I which in turn may be supported on the cabinet I2. To one arm of the bracket I60 is ,pivotally connected the downward extending lever 98 to which is fixed an armature 99 adapted to cooperate with magnet 86. The lower end of lever 88 is provided with a slot I00 to receive a pin IOI at the outer end of a horizontally movable rod I59. The rod I59 is journaled in openings in bracket I60 and intermediate its ends is pivot- I02 to lever I 43. To the inner end of rod I59 is rigidly secured a plate I64 which in turn is connected by a coil spring l to the lever I43 below the pivot I02. A spring I03 is arranged about rod I59 between the lever 98 and one arm of bracket I60 to retract the lever 98 from magnet 86 when the latter is deenergized.

The operation of the modification just described is substantially as follows: With changes in temperatureof space II the volatile fluid in the expansible fluid thermostat increases or becomes reduced in volume, whereby rod 52 and lever 55' are moved to cause bulb 36 to rock.

either to a circuit open or closing position. When the space II tends to rise above a desired low temperature, bulb 36 is moved from the position shown in Fig. 3,'which may be assumed to position, whereby heating element 23 is connected to the source of electrical supply and -the refrigerating efl'ect produced by cooling element I0 is increased. When the space II tends to fall below the desired low temperature, the bulb 36 is moved to its circuit open position whereby heating element 23 is disconnected from the source of electrical supply and the refrigerating efiect produced in space II is reduced.

Each time switch 3| is moved to its circuit closing position the windings 81 of magnet 86 are energized whereby the armature 99 and lever' 98 are attracted toward the magnet. The energization of the magnet causes rod I59 to move toward the right and impart movement to lever I43 and probing member I45. Assuming that cooling element I0 is substantially defrosted and probing member I45 can freely move toward cooling element I0, lever I43 will not rotate and is only displaced laterally. The parts of the control mechanism are so arranged that, with only parallel displacement of lever I43, the lefthand bifurcated arm I42 will not contact pin I4I whereby switch I3I open position.

When switch 3| is moved to its circuit open position magnet v86 is deenergized and spring I 03 becomes effective to retract" lever 98 and armature 99 from magnet 86. This produces lateral movement of lever I43 away from cabinet I2 and probing member I45 is moved away from to a circuit closing will remain in its circuit open position whereby heating element 85 is disconnected from the source of electrical supply. Under these conditions the trap I3I is filled with liquid ammonia and no hot gases can pass into cooling element I0 through conduit 82.

When magnet 86 is energized and a layer of frost 9 of predetermined thickness has formed on cooling element I0, the above described operation is'automatica'lly modified in the following manner: While the rod I59, will move toward the cabinet I2 as before, the movement of probing member I45 toward cooling element I0 is stopped as soon as the enlarged head I68 contacts the layer of frost. Since rod I59 continues to move toward the cabinet I2, lever I43 rotates in a clockwise direction about the pin and slot connection I6I and I82. The lever I43 rotates sufliciently for the left-hand bifurcated arm I42 to contact pin in and cause bulb I36 to rock from its circuit open position shown in Fig. 3 to its circuit closing position. With switch -.I3I moved to its circuit closing position heating element 85 is' connected tothe source of electrical supply and liquid ammonia in trap 8| is evaporated. When the liquid seal in conduit 82 is broken, ammonia vapor flowing upward through conduit 83 can pass through conduit 82 and flow directly into cooling element I0 to heat the latter andcause melting of frost accumulated thereon.

With cooling element I0 at an increased temperature the space II will rise above the desired low temperature, so that switch 3| remains in its closed position and both heating element 23 and magnet 86 will be energized. The operation of the refrigeration system is not suspended, therefore, .as far as expulsion of ammonia vapor in generator 24 99 attracted by magnet 86 and rod I59 moved as far as possible toward cabinet I2, the tension of spring I65 is increased whereby probing member I 45 is constantly urged toward the right with the enlarged head I68 bearing against the frost. Withmelting of frost probing member I45 is movedtoward cooling element I0, and, when the cooling element is substantially defrosted, lever I43 will be moved in a counter-clockwise direction about pivot I02 a distance sufiicient for theright-hand bifurcated arm I42 to contact pin HI and rock bulb I36 to its circuit open position. With switch I3I in its circuit open position, heating element 85 is disconnected from the source of electrical supply and liquid ammonia in condenser 26 will collect in trap 8I to provide the liquid seal and prevent further flow of ammonia vapor through conduit 82 to the upper part of cooling element I0.

Since the space IIv will be above the desired low temperature at the termination of the defrosting period, switch 3I remains in its closed is concerned. With armature with Fig. 3, similar parts being designated by the same reference numerals. The heating element I85, which corresponds to the heating element 05 in Fig. 3, is only shown diagrammatically and is in thermal relation with cooling element I0. The refrigeration system associated with cooling element I may be the same as that shown in Fig. 1. As in Fig. 3, probing member I45 is moved toward cooling element i0 each time switch 3i is closed and magnet is energized. When cooling element It is substantially defrosted, switch I3I remains in its open position and heating element I85 is disconnected from the source of electrical supply. When a layer of frost of predetermined thickness has formed on cooling element I0, movement of probing member I45 stops as soon as it contacts the frost, and, as described above in connection with Fig. 3, switch I3I is closed and heating element I85 is connected to the source of electrical suply. Suificient heating is produced by heating element I85 to raise cooling element I0 above 0 C. to cause melting of frost formed thereon. With the cooling element I0 substantially defrosted, switch I3I is moved to its circuit open position and heating element I85 is disconnected from the source of electrical supply.

While defrosting is taking place, switch 3I is closed and heating element 23 is energized so that defrosting is effected without disturbing the operation of the refrigeration system. When the defrosting operation'is terminated, therefore, the cooling element will become immediately effective to produce refrigeration in space II. With this arrangement defrosting can be effected very rapidly because heat is conducted directly to the cooling element I0.

In Figs. 5 and 6 I have shown a further modifl cation in which a variable operating condition of a part of the refrigeration system is utilized to impart movement from time to time to probing member I 45. The refrigeration system in Fig. 5 is generally the same as that shown in Fig. 3 with similar parts designated by the same reference numerals, and differs therefrom in that a gas burner I04 serves as a source of energy for the system instead of electrical heating element 23.

A'suitable combustible gas is delivered through conduit I05 to burner I04, the flow of gas being controlled by a valve diagrammatically indicated at I00. The valve I 05 is controlled by an expansible fluid thermostat which includes a capillary tube I01 and a thermal element I08 disposed in space II. When the space Ii tends to rise above a desired low temperature, the expansible fluid thermostat causes the-valve I05 to open to increase theflow of gas to burner I04; and, conversely, whenthe temperature of space ii tends to fall below the desired low temperature, the thermostat causes the valve I05 to close to reduce the flow of gas to burner 804.

The burner flame projects into the of a flue I09 which extends upwardly through generator 24. The upper part of fine I09 is provided with a by-pass including conduit I I0, jacket -I arranged about one arm of trap 8i, and conduit H2. The fiow'of combustion gases through the ,by-pass is controlled by a valve 4 which is lower end preferably curved to the shape of the flue to effectively close the lower end of conduit I I0.

The valve H4 is pivotally supported within flue I09 by a pin II5 which extends outside the flue. To the pin I I5 is fixed an arm 6 which in turn is pivotally connected to one end of a lever Ill. The opposite end of lever II! is pivotally connected to a link member II8 which is pivoted at II9'to a suitable support. The lever I I1 is provided with a pin I20 which is in the path of movement of the bifurcated arms I42 at the upper end of lever I 43.

Above the generator 24' is provided a spiralin space II, the size of the burner flame increasesand decreases and hence the temperature of flue I09 varies. When the flow of gas to burner I04 is reduced, for example, the temperature offlue I09 and heating of bi-metallic strip I2I are reduced.

The bi-metallic strip I2I with less heating is arranged to cause movement of rod I23 toward cabinet I2. This imparts movement to rod I59, lever I43, and probing member I45 in the same manner as described above in connection with the control shown in Fig. 3. Conversely, when the flow of gas to burner I04 is increased, the temperature of flue I09 and heating of bi-metallic strip I2I are increased. With increased heating of strip I 2I the bi-metallic strip is arranged to cause movement of rod I23 away from cabinet I 2.

With cooling element I0 substantially defrosted, the lateral displacement of lever I43 with variations of flue temperature takes place without affectingthe valve II4; that is. the left-hand bifurcated .arm I42 of lever I43. does not contact pin I20 on lever II 1 to move valve II4 from its closed position shown in Fig. 5. When a layer of frost of predetermined thickness has formed on cooling element I0. however, and the heating of bi-metallic strip I2I is reduced by lowering of the flue temperature, the movement imparted to rod I59 renders the control mechanism operative to open valve H4 and permit combustion gases to flow through the by-pass and cause heating of liquid ammonia in trap 8!. As in Fig.

3. this is effected by the limited movement of probing member I45 due to its contacting the frost. After movement of probing member I 45 has stopped. the rod I59 continues to move tothe by-pass, ammonia vapor enters cooling elem'ent I0 through conduit 82 to cause melting of frost. The probing member I45 is. constantly bearing against the frost due to the tension in spring I65. and, when the cooling elginent is substantially defrosted and lever I43 has rotated a suilicient distance in a counter-clockwise direcpin I20 and moves lever H1 away from cabinet l2 to cause valve Ill to move to its closed position. This shuts off the flow of combustion gases through the by-pass and liquid ammonia from condenser 26 again collects in trap 8| to provide a liquid seal, whereby normal operation of the refrigeration system is resumed.

By providing a probing member of the character described, defrosting is instigated automatically when the need for defrosting arises and is'also automatically terminated when defrosting is completed. Since the probing member is automatically moved from time to time toward a region of the cooling element-in response to a variable operating condition of the refrigerator, it is not necessary to provide mechanism to predetermine the operation of the refrigerator and adjust any controls to effect such predetermined operatio'n. Instead of utilizing variations in temperature of the space being cooled or the temperature of the generator flue to efiect movement of the probing member, any variable operating condition may be employed, such as, for

example, variations in temperature of the absorber, condenser, or the refrigerant itself.

Although several embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that various modifications and changes may be made without departing from the spirit and scope of the invention. It is therefore contemplated to cover all modifications and changes which come within the spirit of the invention, as pointed out in the following claims.

What is claimed is:

1. Refrigeration apparatus of a continuous absorption type including a cooling element, a generator having a flue, a source of heat for said generator, a device for controlling the source of heat, structure including a member movable toward the cooling element to instigate defrosting when a layer of frost of predetermined thickness has formed on the cooling element, and means for causing said member to move automatically from time to time toward said cooling element with changes of temperature of said flue.

2. Refrigeration apparatus including a cooling element, a member movable toward and away from a-region of said cooling element, a thermostat responsive to the variable temperature condition for caus'mg movement of said member from time to time, and means controlled by said member to cause defrosting of said cooling element'when said member is moved toward said cooling element and a layer of frost of predetermined thickness has formed thereon.

3. A refrigerating system of a continuous absorption type including a' generator, condenser, evaporator and connections therebetween for circulation of refrigerant from said generator through said condenser and into a conduit connected to permit refrigerant to pass from 'said generator to said evaporator and bypass said'condenser, a trap in said conduit adapted to receive liquid refrigerant from said condenser to provide a seal, and means for heating said trap to evaporate liquid therein and permit flow of refrigerant through said conduit from said generator to said evaporator.

4. In a refrigeration system having a cooling element capable of producing a refrigerating effect, the improvement which consists in heating the cooling element to cause melting of frost formed thereon, controlling such heating by a said evaporator,

member adapted to probe from time to time a region of the cooling element upon which frost is normally formed, and imparting movement to said probing member with changes in a variable operatingcondition of the refrigeration system.

5. In a refrigerating system of a continuous absorption type including a generator, condenser, evaporator and connections therebetween for conducting vaporous refrigerant fluid from said generator to said condenser and liquid refrigerant fluid from said condenser to said evaporator, means including a trap to bypass vaporous refrigerant fluid around said condenser from said generator into said evaporator, said trap receiving and holding liquid refrigerant fluid to close said by-pass, and means to reduce the amount of liquid held in said trap to open said by-pass.

6. In a refrigeration system of a continuous absorption type including a generator, condenser, evaporator and connections therebetween for conducting vaporous refrigerant fluid from said generator to said condenser and liquid refrigerant fluid from the latter to said evaporator, means including a trap to by-passvaporous refrigerant fluid around said condenser from said generator to said evaporator, said trap being connected to receive liquid in the system to prevent flow of vaporous refrigerant fluid therethrough, and said trap permitting flow of vaporous refrigerant fluid therethrough when liquid is removed fluid to a place of accumulation and thence to the place of evaporation, flowing vaporous refrigerant fluid to a place of condensation, flowing liquid refrigerant fluid from the place of condensation to the place of accumulation and also to the place of evaporation, and controlling the amount of liquid held in said place of accumulation to permit or prevent flow of vaporous refrigerant fluid therethrough to said place of evaporation.

8. A refrigerating system including a cooling element, and a device operative when a predetermined layer of frost has accumulated on said cooling element to cause flow of hot vaporous fluid in the system into said cooling element to melt frost on the latter.

9. A method of refrigeration which includes maintaining a supply of vaporous refrigerant fluid, condensing vapor from said supply to liquid, evaporating the condensed liquid to produce a refrigerating effect, maintaining a heat source, and utilizing heat from said source to cause transfer of vapor from said supply into the presence of said evaporating liquid to cause rapid rise in temperature and melting of any frost which may have been formed due to said refrigerating effect.

10. A method of refrigeration as set forth in claim 9 which also includes controlling said transfer of vapor by liquid valve action, and carcrating effect, trapping liquid, and releasing the trapped liquid to cause transfer of vapor from said supply into the presence of evaporating condensed liquid to cause rapid rise in temperature and melting of any frost which may have been formed due to said refrigerating efiect,

13. A method of refrigeration as set forth in claim 12 in which the liquid which is trapped is some of the liquid formed by said condensation.

14. A refrigeration system including a source of vaporous refrigerant fluid, a condenser in which said vaporous refrigerant fluid is liquefied, an evaporator connected to receive said liquefied refrigerant, and a heat operated device for controlling flow of vapor from said source of supply to said evaporator.

15. A refrigeration system including .a source of supply of vaporous refrigerant fluid, a condenser, an evaporator, a liquid trap, means for filling and emptying said trap with liquid, and a conduit including said trap for conducting vapor from said supply to said evaporator when the trap is open.

16. A refrigeration system including a source of vaporous refrigerant fluid,'a condenser, an evaporator, a conduit including a liquid trap for conducting vapor from said source to said evaporator, means for supplying liquid to said trap, and means for heating said trap to expel liquid therefrom and thereby control flow of vapor through said conduit. 7

17. A method of refrigeration which includes evaporating liquid refrigerant at a low vapor pressure to produce refrigeration, creating said low vapor pressure by absorption of refrigerant.

fluid vapor into an absorbent, expelling refrigerant fluid vapor from said absorbent, condensing expelled vapor to provide liquid for said evaporation step, and intermittently raising said low vapor pressure by introducing expelled vapor directly from its place of expulsion into the presence-of liquid refrigerant fluid to be evaporated.

ERIK SIGFRID LYNGER. 

